The legislature passed an independence declaration during an extraordinary session, proclaiming the Black Sea peninsula an independent sovereign state, the Republic of Crimea, Xinhua reported.

The declaration appeals to the UN and its member states to recognise its existence and promises to "build its relations with other states on the basis of equality, peace, good neighborliness and other universally recognized principles of political, economic and cultural cooperation."

The parliament has also formally sent an application to the Kremlin to join the Russian Federation as a new republic.

A delegation of Crimean authorities is expected to arrive in Moscow later to discuss the procedure of Crimea's integration into Russia's economic and legal system.

Earlier in the month, the Crimean parliament voted to become part of Russia and passed a resolution of declaration of independence, paving the way for Sunday's referendum.

Ukrainian authorities have dismissed the referendum as "illegal", saying it violated the country's constitution.

"Crimea is a territory of the Ukrainian state. Our citizens reside there. We do not recognise and will never recognise the so-called referendum," Ukrainian Prime Minister Arseny Yatsenyuk said.

Western countries including the US, France, Germany and Britain also rejected the referendum, calling the vote "illegal" and "contrary to the Ukrainian constitution".

US President Barack Obama said the US would not recognise the Crimean referendum and vowed to impose fresh sanctions on Russia.

In his talks with Russian President Vladimir Putin over the phone, Obama said the vote in the Ukraine's autonomous republic violated the Ukrainian constitution, Xinhua quoted the White House as saying Sunday.

It was also held "under duress of Russian military intervention", Obama said.

He told Putin that "Russia's actions were in violation of Ukraine's sovereignty and territorial integrity and that, in coordination with our European partners, we are prepared to impose additional costs on Russia for its actions".

Putin refused to back off.

"Putin said the Crimean population's vote is proceeding in full compliance with international law," the Kremlin web site said, citing the telephone conversation between the leaders.

"Russia will respect the choice of Crimean residents," Putin said, adding that he was concerned about the aggravation of the situation in eastern and southeastern regions of Ukraine.

But Putin and Obama agreed to continue searching for ways to restore stability in Ukraine.

Washington has canceled trade talks and military exchanges with Russia, and Obama has authorised visa bans and freezing of assets of some Russians and Ukrainians blamed for Moscow's military takeover of Crimea.

Putin told German Chancellor Angela Merkel earlier that Russia would "respect the choice" of the Crimeans.

Merkel, however, underscored the urgency of holding direct talks between Russia and Ukraine, a German government spokesperson said.

The German chancellor said the existing presence of the Organisation for Security and Cooperation in Europe (OSCE) in Ukraine should be quickly expanded.

She stressed that it was urgent and necessary for the governments of Russia and Ukraine to hold direct talks.

Washington and its allies have been pushing for Moscow to withdraw its military personnel posted in bases in Crimea, home to Russia's Black Sea Fleet, allow international monitors into Crimea and to open a dialogue with the Ukrainian government.

French Foreign Minister Laurent Fabius denied the legitimacy of Crimea's referendum, urging Russia to take immediate measures to avoid a "useless" and "dangerous" escalation of Ukrainian crisis.

"Nothing in the way that the referendum has been conducted should convince anyone that it is a legitimate exercise," British Foreign Secretary William Hague said.

The European Union said the referendum in Crimea was "illegal and illegitimate" and its outcome "will not be recognised".